Purpose: This study has for objective the assessment of the vigilance, mood states variations and the blood glucose levels, during a triangular effort progressive in trained athletes during Ramadan fasting (RF). Methods. Ten trained male athletes aged 21.8 ± 1.1 years are evaluated before (B.RF), during (1st, 2nd and 3th week) and after Ramadan fasting, in the blood-glucose, vigilance, and mood states at rest and after (A. Ex. ) a triangular exercise test (TUB II).Results. Comparing to the reference period (B.RF), the RF induces a decrease in the maximal aerobic power (TUB II) approximately 2-Cleanup Messy Code 5% and a hypoglycaemia. The objective vigilance is doubly influenced by the RF (F= 14.58, p<0.002) and the exercise (F = 13.04, p<0.02), and decreasing significantly during the 1st and 2nd week of RF. However the subjective vigilance and moods states are not varied neither by the RF nor by the exercise.Conclusion. The results should guide the work of physical education teachers and coaches to a programming by integrating more of periods of complete recovery, and avoiding risky tasks requiring sustained attention.